Monitoring pressurized vessels for leaks, ruptures or hard hits

• US 5,623,421 A
• Filed: 11/03/1995
• Issued: 04/22/1997
• Est. Priority Date: 11/03/1995
• Status: Expired due to Fees

• Current Assignee: Rensselaer Polytechnic Institute
• Original Assignee: Rensselaer Polytechnic Institute
• Inventors: Savic, Michael
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): MILLER, CRAIG S
• Application Number:
  US08/552,542
• Time in Patent Office: 536 Days
• Field of Search: 367/117, 376/252, 73/52, 73/584, 73/587, 73/659, 73/40, 73/40.5 R, 73/40.5 A, 73/49.2, 73/570, 73/592, 73/579, 73/49.3, 340/603, 340/605, 364/506, 364/509, 364/510
• US Class Current: 702/51
• CPC Class Codes: G01M 3/24 using infrasonic, sonic, or ultrasonic vibrations
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/105 two or more emitters, two or more receivers
• CPC Class Codes: G01N 29/12 by measuring frequency or resonance of acoustic waves measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00

Abstract

A device monitors a pressurized vessel to detect small leaks, ruptures and hard hits on the vessel. Transducers are attached to the vessel and transmit acoustic signals which are processed to extract frequency spectra which contain dominant resonant frequency peaks, if the vessel contains a small leak. If multiple frequency component of the spectra shift to a lower frequency suddenly and stay at the lower frequency, this indicated the presence of a larger leak or rupture. A hard hit on the vessel, for example by machinery, is detected by a shift in the transient response of harmonics in the acoustic signal.

Claims

1. A device for monitoring a pressurized vessel for an occurrence of small leaks or ruptures or hard hits, comprising:

a plurality of acoustic transducers at spaced sensor locations on the vessel, each responsive to sounds from the vessel at each sensor location, to generate acoustic signals from each sensor location; and

a central processor connected to each of said transducers and including spectra means for repeatedly recording a frequency spectrum of the acoustic signal from each transducer, the frequency spectrum being selected to contain the dominant resonant frequencies of the vessel, the central processor including program means containing a dominant resonant frequency for the vessel and analysis means for detecting peaks in each spectra at the dominant frequency, the presence of peaks indication the existence of a small leak in the vessel.

2. A device according to claim 1, wherein the central processor comprises a digital computer programmed to form the spectra means and the analysis means.

3. A device according to claim 1, wherein each spectrum contains multiple frequency components, said analysis means including means for detecting a shift of the multiple frequency components to a lower frequency, and a remaining of the multiple frequency components at the lower frequency, which indicates a rupture in the vessel.

4. A device according to claim 1, including means for determining an amplitude of a plurality of harmonics of the acoustic signal and means for detecting a transient response of the harmonics which is an indication of a hard hit on the vessel.

5. A device according to claim 1, wherein the acoustic transducers are each a mechanical transducer containing a resonant gate transistor.

6. A device according to claim 5, wherein each transducer comprises a cantilevered gate electrode connected to an input plate for receiving acoustic signals from the vessel.

7. A device for monitoring a pressurized vessel for an occurrence of a rupture, comprising:

at least one acoustic transducer on the vessel and responsive to sounds from the vessel to generate acoustic signals; and

a central processor connected to said transducer and including spectra means for repeatedly recording a frequency spectrum of the acoustic signal, the frequency spectrum being selected to contain the dominant resonant frequencies of the vessel, each spectrum containing multiple frequency components, the central processor including analysis means for detecting a shift of the multiple frequency components to lower frequency and a remaining of the frequency components at the lower frequency, indicating a rupture in the vessel.

8. A device according to claim 7, wherein the acoustic transducer comprises a mechanical transducer containing a resonant gate transistor.

9. A device for monitoring a pressurized vessel for an occurrence of a hard hit, comprising:

at least one acoustic transducer on the vessel, responsive to sounds from the vessel to generate acoustic signals;

a central processor connected to said transducer and including means for recording dominant harmonics such as the first, second and third harmonics of the acoustic signal from the transducer, the central processor including analysis means for detecting a transient response of the harmonics which is indicative of a hard hit to the vessel; and

a plurality of phase locked loops, each tuned to a different harmonic of the acoustic signal, said phase locked loops being connected to the at least one acoustic transducer for receiving the acoustic signal therefrom, a delay circuit connected to each phase locked loop for delaying the acoustic signal by different amounts of time and addition means connected to the delay circuits for adding delayed acoustic signals to each other to detect the transient response.

10. A device according to claim 9, wherein the device includes three phase locked loops, one tuned to the first harmonic, another tuned to the second harmonic and a third tuned to the third harmonic, each of the delay circuits generating a delay pulse having a different duration for detecting the transient response.

11. A device according to claim 9, wherein the acoustic transducer comprises a mechanical transducer containing a resonant gate transistor.

12. A device for monitoring a pressurized vessel for the occurrence of small leaks, ruptures or hard hits comprising:

a cantilevered gate electrode;

an input force plate connected to the vessel and to the cantilevered gate electrode for receiving an acoustic signal from the vessel and transmitting it to the cantilevered gate electrode;

electric signal generating means connected to the gate electrode for generating an electric signal correspondent to the acoustic signal; and

processing means connected to the signal generating means for producing a frequency spectrum corresponding to the acoustic signal and at in a range of frequencies containing dominant resonant frequencies of the vessel, the processing means including means for containing a dominant resonant frequency for the vessel and analysis means for detecting peaks in each frequency spectrum at the dominant frequency, the presence of peaks indicating the existence of a small leak in the vessel.

13. A device according to claim 12, wherein the processing means comprises analysis means for detecting a shift of multiple frequency components to lower frequencies in each frequency spectrum, and a remaining of the multiple frequency components at the lower frequency, the shift and remaining of the frequency components at the lower frequency indicating a rupture in the vessel.

14. A device according to claim 12, wherein the processing means includes means for determining an amplitude of a plurality of harmonics of the acoustic signal and means for detecting a transient response of the harmonics which indicates a hard hit on the vessel.

15. A device according to claim 14, wherein said means for determining an amplitude of a plurality of harmonics of the acoustic signal comprise a plurality of phase locked loops, each tuned to a different harmonic of the acoustic signal, each phase locked loop being connected to the signal generating means, the means for detecting a transient response comprising a plurality of delay circuits, each connected to one of the phase locked loops for applying a different dealy to the output of each phase locked loop, and an addition circuit connected to each of the delay circuits for adding the outputs of the delay circuits to each other for detecting the transient response.